Vigor and tolerance of cowpea (Vigna unguiculata) genotypes under salt stress

Abstract

Saline stress is a frequent phenomenon in the arid and semi-arid regions of the globe, affecting the agricultural production of these regions, and it is necessary to use strategies that minimize the impacts of saline stress under agriculture. This requires the incorporation of species, variety and genotypes tolerant to increase agricultural production in those regions. This study aimed to evaluate germination and initial growth of cowpea genotypes under salt stress. The experimental design was completely randomized in 19 x 3 factorial scheme, composed of nineteen cowpea cultivars and three osmotic potentials, with four replicates of 50 seeds each. The germination test lasted for eight days, when the seeds were evaluated for germination percentage, germination speed index, length of shoot and root, accumulation of dry mass of shoot and root. The increase in salinity affected germination and initial growth of the cowpea genotypes. The genotypes 6 -MNCO2-689F-2-8, 10 -MNCO2-675F-4-10, 12 -MNCO3-737F-5-9, 16 -MNCO2-677F-2, 18 -BRS-Pajeú and 19 -Paulistinha exhibited higher tolerance to salt stress in the stage of germination and initial growth. The genotypes 11 -MNCO2-675F-9-5, 13 -BRS-Tumucumaque, 15 -MNCO3-736F-7 and 17 -BR17-Gurgueia were more susceptible to the effects of salt stress in the stage of germination and initial growth.

Tolerance of seedlings traditional varieties of cowpea (Vigna unguiculata) to salt stress

“…Table 3 shows that the varieties 1 Canapu Vermelho, 3 Pingo de Ouro, 4 Sempre Verde, 7 Manteiga, 17 Sempre Verde Ligeiro, and 18 Vagem Roxa showed reduction in shoot dry mass accumulation as water salinity increased, with reductions of up to 59.6% that in variety 4 Sempre Verde. Reductions in root dry mass in the presence of salts in the soil solution negatively affect nutrient absorption and, consequently, the accumulation of shoot dry mass, which has also been observed in other studies (Coelho, Agostini, Guaberto, Machado, & Custódio, 2010;Gomes et al, 2015;Sá et al, 2017b).…”

“…This fact indicates that salt stress affected the accumulation of carbohydrates in cowpea seedlings. This is possibly due to the reduction of reserve polysaccharides and the degradation of hydrolytic enzyme activity (cotyledons) (Sá et al, 2017b). Other reductions in dry mass accumulation in cowpea seedlings under salt stress have also been found by Santos et al (2009) and Almeida et al (2012).…”

“…In a general analysis of emergence percentage and speed index of the varieties under conditions of high salinity, traditional varieties 5 Ceará, 6 Baeta, and 23 Paulistinha showed the best performance in the emergence stage (Table 3). This occurred because of the capacity of some genotypes to perform osmotic homeostasis, which favors the hydration of tissues at osmotic potentials that are unfavorable to the species (Syvertsen & Garcia-Sanchez, 2014;Sá et al, 2017b). In a study about salt stress on cowpea germination, Sá et al (2016) observed that there was no difference between levels of irrigation water salinity (0.0 to 8.0 dS m -1 ) in the germination of the cultivars Paulistinha and Canapu Branco, while other varieties, such as Pingo de Ouro and Costela de Vaca, were affected in the germination stage.…”

“…In studies conducted in the germination stage, Sá et al (2016Sá et al ( , 2017b found that the salinity tolerance of cowpea is variable among varieties, genotypes, and strains of this species. Thus, the objective was to study the tolerance of traditional varieties of cowpea to irrigation water salinity in the emergence and initial growth stage.…”

Hydric and saline stress on Phaseolus lunatus L. seeds

“…The Phaseolus lunatus L. is one of the most important legume crops of tropical regions worldwide, and in northeastern Brazil, where the bean is commonly known as 'feijão-fava', the species is both economically and socially important, owing to its ability to tolerate arid conditions, high temperatures, low and erratic rainfall, low-fertility soil, and high salinity (Nascimento et al, 2017). Indeed, drought and salinity are the primary factors that limit the germination of many crop species in arid and semi-arid regions (Patanè et al, 2013).…”